Virtual metrology (VM) generally refers to a model-based prediction of some process outcome in place of, or in the absence of, an actual physical measurement of that outcome. The underlying models are learned from histories of the actual physical outcomes and predictors that may include process trace data, tool consumable status, and incoming work characteristics, among other factors. If the models are sufficiently accurate predictors of process outcomes, VM applications present an opportunity to reduce the number of physical measurements made to monitor a given process, while maintaining or even improving quality control. Such applications are especially attractive for highly complex, capital-intensive semiconductor manufacturing lines in which measurements monitoring processes may add significant processing time and cost.